F_Lim_R - Siemens SIMATIC S7 F Manual

Fail-Safe Blocks
8.13.9

F_LIM_R

Function
This block compares the input variables IN, MAX and MIN. It checks whether IN is
within or outside the interval between MIN and MAX. If the lower limit (MIN) of the
interval is greater than or equal to the upper limit (MAX), the output OUT = MAX
and the outputs OUTU and OUTL are set to 1. If IN is > MAX or IN represents a
positive overflow, the upper limit has been violated, OUT = MAX, OUTU = 1 and
OUTL = 0. If IN is < MIN or IN represents a negative overflow, the lower limit has
been violated, OUT = MIN, OUTU = 0 and OUTL = 1. If IN is between MIN and
MAX, OUT = IN, OUTU = 0 and OUTL = 0 are set.
If the input variable (IN) contains an invalid REAL number, the Substitute Input
(SUBS_IN) will be passed directly to the output (OUT) and both OUTH=1 and
OUTL=1.
I/Os
Name
Inputs:
IN
MIN
MAX
SUBS_IN
Outputs:
OUT
OUTU
OUTL
Error Handling
In the event of an error that is critical to safety, the system function SFC F_CTRL is
called. This records the event in the Diagnostic Buffer and requests a switch to the
reserve CPU if the error occurred only on the master CPU. For non-redundant
systems or a common-cause error occurring in both CPUs, the shutdown logic can
be configured to either disable the erred F-run-time group or the entire Safety
Program.
Error Information in Diagnostic Buffer
Error Code (W#16#...)
75D9H
75DAH
Fail-Safe Systems
A5E00085588-03
Data Type Explanation
F_REAL Input variable
F_REAL Lower limit
F_REAL Upper limit
F_REAL Substitute Input
F_REAL Output variable
F_BOOL Upper limit violation
F_BOOL Lower limit violation
Description
Invalid REAL number generated during the calculations
involving IN, MIN, MAX.
Error in the safety data format of the inputs IN, MIN, MAX,
SUBS_IN.
Default
0.0
-100.0
100.0
0.0
0.0
0
0
8-123